Abstract
We evaluate the spectral performance of a novel continuous-wave room-temperature distributed feedback quantum cascade laser operating at the longwavelength of 17 μm. By demonstrating broadband laser absorption spectroscopy of the ν2 fundamental vibrational mode of N2O molecules, we havedetermined the spectral range and established the spectroscopic potential of this laser. We have characterized the frequency noise and measured theline width of this new device, uncovering a discrepancy with the current consensus on the theoretical modeling of quantum cascade lasers. Our resultsconfirm the potential of such novel narrow-line-width sources for vibrational spectroscopy. Extending laser spectroscopy to longer wavelength is afascinating prospect that paves the way for a wide range of opportunities from chemical detection, to frequency metrology as well as for exploringlight-matter interaction with an extended variety of molecules, from ultra-cold diatomic species to increasingly complex molecular systems.